Orthodontic brackets attached to teeth are adapted to engage an archwire that exerts forces upon them to move the teeth. Such brackets typically include an archwire slot for reception of the archwire. An archwire slot can have any desired cross-sectional configuration or size to match requirements of the archwire, or archwires, that are to be engaged within the slot.
Orthodontic brackets are typically bonded to a tooth or to a tooth band with the archwire slot oriented parallel to the occlusal plane. However, the slot can also be angularly oriented across the bracket when desired.
Most brackets in use today include extensions that project upwardly and downwardly at the top and bottom of the installed bracket, respectively. These extensions permit the archwire to be held within the archwire slot of the bracket by means of a twisted wire (ligature) or an elastomer O-ring.
Numerous attempts have been made to design brackets that are self-locking or ligatureless. A detailed discussion of patents and publications describing various closures that have been proposed for the archwire slots of such orthodontic brackets can be found in U.S. Pat. No. 5,094,614 to Wildman, issued Mar. 10, 1992, which is hereby incorporated into this disclosure by reference.
As recognized in the Wildman patent, an ideal locking device for an orthodontic bracket should leave the top and bottom of the bracket, including the projections conventionally used for anchoring the tying wires, free to receive other attachments or auxiliary devices.
The Wildman patent discloses a slidable closure that engages the front of the archwire. The closure is recessed from the front or anterior surfaces of the disclosed bracket. This is also true of sliding closures shown in U.S. Pat. No. 2,671,964 to Russell et al., which was issued on Mar. 16, 1954 and in U.S. Pat. No. 3,131,474, which was issued on May 5, 1964 to Johnson. The fact that such recessed sliding closures require the archwire also to be recessed within the archwire slot before the closure can be moved over the archwire makes it very difficult for the user to visually confirm that the archwire is properly seated within the archwire slot to facilitate closing of the slidable cover.
When using a conventional bracket and tying wires, proper seating of the archwire can be confirmed by visually noting that the anterior surface of the archwire is flush with the anterior surface of the bracket. It is desirable that a self-locking bracket provide similar visual reference capabilities to the user. This cannot be attained where a sliding closure is recessed within the bracket.
A flush-mounted closure in the form of a spring clip is shown in various embodiments illustrated within U.S. Pat. No. 4,023,274 to Wallshein, issued on May 17, 1977. In FIGS. 4A and 4B of the Wallshein patent, there is illustrated a spring clip having a closure panel that extends across the full width of a bracket and covers aligned slots in two separate lugs. However, the spring clip also covers the bottom of the bracket and presents a separable bracket element that must be attached to the bracket prior to its utilization. A sliding closure is more easily manipulated than a spring clip. Slidable closures are particularly desirable because they substantially reduce the time required for opening and closing of the archwire slots during periodic adjustment of the archwire and brackets.
The present bracket was designed to mount an archwire flush with the anterior surface of an orthodontic bracket to facilitate visual positioning of the archwire during orthodontic treatment. It also was designed to utilize a sliding closure that is permanently retained on the bracket during use, whether the closure is left in an open or closed condition. This guards against accidental release of the closure while the bracket is worn on a tooth.
Most importantly, the closure has been designed to leave the usual tying extensions that protrude from the top and bottom of the bracket fully accessible to other orthodontic attachments to apply torsional forces to the teeth. The exposed tying lugs remain always available for repositioning of the bracket and tooth by use of tying wires or other conventional attachment systems.
The present bracket also includes a closure that completes a continuous tube surrounding the archwire when the closure is in a closed position. This can be effectively achieved in a Siamese bracket configuration without covering or interfering with projecting extensions on the bracket.
Creation of a continuous tube surrounding the archwire across the full width of the bracket eliminates the binding of the archwire within the confines of the bracket which occurs across the corners typically presented by conventional slotted bracket lugs.
In addition, the present closure lends itself to applications where the projecting lug structure of the bracket is angularly situated on a supporting base. By using a common lug structure on brackets having a plurality of archwire slot angles, a common closure can be used regardless of the slot angle. This substantially reduces the cost of producing the multiple brackets needed for orthodontic treatment purposes.